in international relations, the relationship between two states one of which exercises some decisive control over the other. The degree of control may vary from a situation in which the protecting state guarantees and protects the safety of the other, such as the status afforded to the kingdom of Bhutan by India, to one that is a masked form of annexation, in the manner of the German protectorate established in Czechoslovakia in March 1939.

The use of the term protectorate to describe such a relationship is a recent one, dating from the 19th century. Nevertheless, the relationship is an ancient one. The kingdoms of Numidia, Macedonia, Syria, and Pergamum were examples of protected states under the control of Rome. In the 16th century the rise of European national states led to increasing use of the system of protectorates as a prelude to annexation, particularly by France. This use was also developed during the 19th century as a means of colonial expansion or as a means of maintaining the balance of power. Thus, by the Treaty of Paris (1815) the Ionian Islands became a protectorate of Great Britain in order to prevent Austria from gaining complete control of the Adriatic Sea. Later in the century, a curious situation arose with the disintegration of the Ottoman Empire. Provinces that owed allegiance to Turkey began to revolt against Turkish rule and, as a stage in their struggle for independence, were sometimes placed under the protection of a foreign power. Thus, Moldavia and Walachia, which became protectorates of Russia in 1829, were placed under international protection in 1856 and in 1878 united to form the independent state of Romania.

In modern times, the majority of protectorates have been established by treaty by the terms of which the weaker state surrenders the management of all its more important international relations. The treaty defines the position of the protected state in the international community, with special reference to its treaty-making powers and its right to diplomatic and consular representation. The right of the protecting state to interfere in all matters of external affairs constitutes a definite loss of sovereignty on the part of the weaker state.